The present invention relates to a method for joining a first component to a second component at a joining site of the first component, the first component having at least an essentially planar first structural element, an essentially planar second structural element, and a plastic-containing intermediate layer disposed at least in certain regions between the two structural elements.
The present invention also relates to a structural element composite including a first component and a second component that is joined to the first component at a joining site thereof.
The present invention also relates to a device for preparing a joining site on a first component to join the first component to a second component at the joining site of the first component.
Lightweight design concepts based on aluminum materials or composite sheet-metal components, for example, are known in automobile manufacturing. Combining high strength steels for crash-related components with multilayer composite panels for large-area components results in a lightweight design concept that is more economical than aluminum materials, particularly in body manufacturing. Composite panels are typically made of thin, for example, of 0.2 mm to 0.3 mm steel cover plates and of a plastic-containing intermediate layer made of thermoplastic plastic, for example, typically having a thickness of between 0.2 mm and 1.5 mm. The weight per unit area is thereby appreciably less than other known automotive body sheet metals. Another advantage of such composite sheet-metal components is the high flexural strength thereof.
The intermediate layer disposed between the two thin steel cover plates is electrically insulating and, thus, not suited for resistance welding, arc welding or beam welding. It is, therefore, necessary to improve mass-production joining technologies to enable such composite sheet-metal components to be used in body manufacturing. However, thermal joining processes cannot be employed with high process reliability because of the intermediate layer. The high process temperatures cause considerable foaming and spattering, and damage to the composite sheet-metal component. Also, sheet metal-type components and functional elements, for example, fastening elements, such as bolts and nuts cannot be integrally attached because of the intermediate layer. The intermediate plastic layer reduces the joining strength when functional elements, for example, fastening elements, are mechanically joined. The clamping force produced in the joining process between the composite sheet-metal component and a functional element can be reduced by creep processes in the intermediate layer material at temperatures within the range of approximately 180° in the cathodic dip painting process.
Therefore, today's state of technological development dictates that sheet metal-type components preferably be mechanically joined to the composite sheet-metal component. Joining methods for joining composite sheet-metal components to functional elements, for example, fastening elements, such as bolts and nuts, are not yet known under the related art.
To weld together multilayer composite panels, the German Patent Application DE 101 11 567 A1 already describes manufacturing components partially without an insulating intermediate layer. Resistance spot welding can be used at those locations.
The German Patent Application DE 10 2011 054 362 A1 describes a method for manufacturing a composite sheet-metal component having a metallic edge region; the component having two outer cover plates of metal and at least one layer made of a plastic disposed therebetween.
To prepare a joining site, the International Patent Application WO 2013/020 636 A1 describes a method for joining sheet metal-type structural elements having an intermediate layer of thermoplastic plastic. It provides for melting and displacing the intermediate layer in certain regions and for producing a material-to-material bond of the two structural elements by welding. For this, upon displacement of the intermediate layer, a welding current is applied in one region until at least one of the two structural elements is heated to above the melting point thereof and partially liquefies. A material-to-material bond can be produced in this way between the two structural elements.